Gene-rich UV sex chromosomes harbor conserved regulators of sexual development

Abstract

Nonrecombining sex chromosomes, like the mammalian Y, often lose genes and accumulate transposable elements, a process termed degeneration. The correlation between suppressed recombination and degeneration is clear in animal XY systems, but the absence of recombination is confounded with other asymmetries between the X and Y. In contrast, UV sex chromosomes, like those found in bryophytes, experience symmetrical population genetic conditions. Here, we generate nearly gapless female and male chromosome-scale reference genomes of the moss Ceratodon purpureus to test for degeneration in the bryophyte UV sex chromosomes. We show that the moss sex chromosomes evolved over 300 million years ago and expanded via two chromosomal fusions. Although the sex chromosomes exhibit weaker purifying selection than autosomes, we find that suppressed recombination alone is insufficient to drive degeneration. Instead, the U and V sex chromosomes harbor thousands of broadly expressed genes, including numerous key regulators of sexual development across land plants.

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© 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC). https://creativecommons.org/licenses/by-nc/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial license, which permits use, distribution, and reproduction in any medium, so long as the resultant use is not for commercial advantage and provided the original work is properly cited.

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Keywords

Ceratodon purpureus, Sex Chromosomes

Citation

Carey, S. B., Jenkins, J., Lovell, J. T., Maumus, F., Sreedasyam, A., Payton, A. C., Shu, S., Tiley, G. P., Fernandez-Pozo, N., Healey, A., Barry, K., Chen, C., Wang, M., Lipzen, A., Daum, C., Saski, C. A., McBreen, J. C., Conrad, R. E., Kollar, L. M., . . . McDaniel, S. F. (2021). Gene-rich UV sex chromosomes harbor conserved regulators of sexual development. Science Advances, 7(27), eabh2488. https://doi.org/10.1126/sciadv.abh2488

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